Print all messages from all authors under `refs/heads/*` newer than those under `refs/delivered/*`(all if `refs/delivered/*` do not exist) in causal order, then update `refs/delivered/*` to reference the same messages as `refs/heads/*`.
Print all messages from all authors under `refs/heads/*` newer than those under `refs/delivered/*` in causal order, then update `refs/delivered/*` to reference the same messages as `refs/heads/*`.